The present invention relates to a technology for fabricating liquid crystal panels equipped with glass substrates for holding liquid crystal.
Conventionally, liquid crystal panels hold liquid crystal between two glass substrates. For example, in thin-film transistor (TFT) panels, a color filter, transparent electrodes, and thin-film transistors are formed on the glass substrates and a roughly constant gap is maintained between the glass substrates by spacers. The liquid crystal filling the space between the substrates is kept in a sealed state by a sealing material. Thus, in producing liquid crystal panels a sealing material is disposed on at least one of the two glass substrates to surround the area that will be filled by the liquid crystal. Then, the two glass substrates are processed to form a composite structure. In this processing, spacers uniformly come into contact with the two glass substrates, and the sealing material is squeezed between the substrates in the display area and hardened so that a uniform gap is formed. After the sealing material is hardened, the liquid crystal is placed into the region surrounded by the sealing material. In the conventional technology, if a thermosetting resin is used as the sealing material, the gap between the two glass substrates is usually formed using one of the following three methods. (1) Two flat heaters are placed on either side of the glass substrates and pressure is applied. (2) The glass substrates are placed on a plate and a sheet is covered and sealed over this. Air is discharged to form a vacuum so that the pressure difference with atmospheric pressure causes pressure to be applied to the glass substrates. The substrates are heated by a heater disposed on the plate, a hot-air furnace, or the like. (3) The glass substrates are covered and sealed from either side by sheets. A vacuum is formed so that the pressure difference with the atmospheric pressure causes pressure to be applied to the glass substrates. The substrates are heated with a hot-air furnace or the like.
In method (1), larger substrate areas require application of greater pressure, thus making the device larger. As a result, the method is not suited for clean-room production. Also, the glass substrates are rapidly heated and pressurized so that the discharge of air from between the glass substrates may not be performed quickly enough, resulting in variations in the gap between the substrates. Also, if the pressure is increased to promote discharge of air, the internal pressure increases, causing the sealing material to pop or offsets to be generated between the glass substrates. In method (2), if the plate is heated ahead of time, the one-sided application of heat results in a temperature difference between the glass substrates. Differences in thermal expansion can lead to warping and shifts in the glass substrates. Also, if the plate is heated after the glass substrates are mounted, the heating of the plate itself takes time. The same issues apply if a hot-air furnace is used. Method (3) also involves a delay for heating.
It is an object of the present invention to provide a liquid crystal panel technology that can overcome the problems described above.